So I always find ways to make the ESX servers angry. They are always stupid in hindsight. So the first easy way is to attempt to snapshot a VM that has very little space. It will start the snapshot and then run out of space, pausing your VM. And then joy, your vm is not working anymore. It tends to stall out the virtual center and won’t let you shut down the VM either. If you are patient, you can restart the virtual center. Then eventually get the VM shutdown, and then you can remove the snapshot. If you are lucky it will let you start it up again.

Another really fun way to make ESX angry is to delete an iscsi volume that it is actively using (deleting it on the SAN side) if you are stupid enough to do this (like me) you will see BAD THINGS like this http://communities.vmware.com/thread/228586